Electro-pneumatic air brake valve and system compatible with a skid control system

ABSTRACT

A vehicle brake actuation system is disclosed containing fluid pressure to operate brake actuators for effectively combining an electro-pneumatic relay system to function with a skid control system. A first valve is connected in the system for releasing a first impulse of fluid pressure from a first container. A second valve is connected to receive the first impulse from the first container, a second pressure impulse from a second container and to release a thrid pressure impulse from the second container to the actuators. A first sensor senses fluid pressure between the first and second valves and produces a first signal in proportion thereto. A second sensor senses fluid pressure between the second valve and the actuators and produces a second signal in proportion thereto. A first logic circuit receives and compares the first and second signals for discriminately controlling communication of the first, second and third impulses with the second valve. A second or skid control logic circuit is operable to override the first logic circuit to discriminately interrupt communication of the first impulse with the second valve. The second valve has a first port for receiving the first impulse. A second port is connected to receive the second impulse. A first solenoid in the first port is normally open and is operable to close for interrupting the first impulse. A second solenoid is in the second port and is normally closed and operable to open for admitting the second impulse to the valve.

This is a division of application Ser. No. 536,596, filed Dec. 26, 1974.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates generally to fluid pressure brake systems andparticularly to automatic application valves as used in such systems.

2. Description Of The Prior Art

In air brake systems, especially in tractor-trailer combinations, aproblem exists in that air pressure applied at the tractor portion mustactuate the trailer brakes which are physically located substantialdistances from the tractor. As a result, time delays exist between theair brake application at the tractor and air brake actuation at thetrailer. To reduce such time delays, valves and systems were devisedwhereby an air supply was provided in proximity to the trailer brakesand a relay valve was provided adjacent that air supply. In addition,since an electrical impulse can move between two points faster than animpulse moved by air pressure, electrical means were provided to actuatethe relay valve for releasing air pressure to actuate the trailer brakesinasmuch as electrical signals could actuate the trailer brakes almostsimultaneously with application of the brakes at the tractor thusavoiding the previously known time delays. Such systems are of the typeshown and described in U.S. Pat. Nos. 3,747,992 and 3,796,468.Unfortunately, the systems of the prior art are not compatible with skidcontrol systems unless a novel relay valve is provided in the system.

SUMMARY OF THE INVENTION

Accordingly, the present invention provides a system and a valve for usetherein to make that system compatible with skid control systems intractor-trailer combinations. The foregoing is accomplished by providinga vehicle brake actuation system for containing fluid pressure tooperate brake actuators for effectively combining an electro-pneumaticrelay system to function with a skid control system. Specifically, afirst valve is connected in the system for releasing a first impulse offluid pressure from a first container. A second valve receives the firstimpulse from the first container, a second pressure impulse from asecond container and releases a third pressure impulse from the secondcontainer to some of the actuators. A first sensor senses the fluidpressure between the first and second valves and produces a first signalin proportion thereto. A second sensor senses fluid pressure between thesecond valve and the actuators and produces a second signal inproportion thereto. A first logic circuit receives and compares thefirst and second signals for discriminately controlling communication ofthe first, second and third impulses with the second valve. A second orskid control logic circuit is operable to override the first logiccircuit to discriminately interrupt communication of the first impulsewith the second valve. The second valve has a first port for receivingthe first impulse. A second port is connected to receive the secondimpulse. A first solenoid in the first port is normally open and isoperable to close for interrupting the first impulse as upon commandfrom either the first logic circuit or from the skid control logiccircuit. A second solenoid is in the second port and is normally closedand operable to open for admitting the second impulse to the valve uponcommand from the first logic circuit.

Other advantages and novel features of the invention will becomeapparent from the following detailed description of the invention whenconsidered in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings wherein like parts are marked alike:

FIG. 1 is a diagrammatic illustration of the system of this invention;

FIG. 2 is a partially cutaway side elevation of the novel relay valve ofthis invention;

FIG. 2a is an exploded partial side elevation of the lower housing ofFIG. 2;

FIG. 3 is a cutaway plan view of the novel relay valve of this inventiontaken along line 3--3 of FIG. 2;

FIG. 4 is a diagrammatic illustration of the first logic circuit of thisinvention; and

FIG. 5 is a graphical illustration of the deadband effect included inthis invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT

FIG. 1 illustrates an electro-pneumatic air brake system generallydesignated 10 which comprises a first portion 12 mounted on the tractorof a tractor-trailer combination and a second portion 14 mounted on thetrailer. Electro-pneumatic air brake systems are well known andgenerally include various interconnected electrical and fluid operatedcomponents including contained sources of fluid, such as air, underpressure.

Tractor portion 12 includes first or application valve 16 having a footpedal 64 to be actuated or depressed by the vehicle operator. Air iscontained under pressure in first reservoir 18. Conduit 20 interconnectsreservoir 18 and valve 16. Also, conduit 28 interconnects reservoir 18and tractor relay valve 26. Conduit 24 guides control air to relay valve26 to actuate valve 26 to apply air to the rear tractor brakes andconduit 30 guides air from relay valve 26 to the rear tractor brakes asshown in the drawing. Conduit 23 delivers air from relay valve 26 to thefront tractor brakes. Conduit 38 interconnects first reservoir 18 withsecond or trailer reservoir 36 so that the tractor and trailer fluidpressure systems can reach an equilibrium pressure. Conduit 22interconnects first or application valve 16 with first port 72 of secondor trailer relay valve 40. First transducer 42 is provided along conduit22 adjacent valve 16 to sense pressure in that conduit and convert thepressure sensed into an electrical signal for sending that signal alongelectrical connector 44 to first logic means or electronic control 46 oftrailer portion 14. Air conduits 22, 38 are continued at thetractor-trailer interface by well known gladhands connectors 34, 32,respectively.

Trailer portion 14 includes relay valve 40. In addition to air suppliedto first port 72 of relay valve 40 from first reservoir 18 of tractorportion 12, second reservoir 36 supplies air to second port 74 of relayvalve 40 via conduit 70. Also, air may be supplied from reservoir 36 toanother portion of relay valve 40 via conduit 68 and ultimately to someof the brake actuators such as the rear trailer brakes via conduit 48.First logic means 46 is electrically connected to a first solenoidadjacent first port 72 of relay valve 40 via electrical connector 62 andto a second solenoid adjacent second port 74 of relay valve 40 viaelectrical connector 60. Second transducer 50 is provided along conduit48 adjacent valve 40 to sense pressure in the conduit and convert thepressure sensed into an electrical signal for sending that signal tofirst logic means 46 via electrical connector 52. Second or skid controllogic means 54, well known, receives input sensor signals from thevehicle wheels via electrical connector 66 to determine impending skidconditions. A skid control output logic signal is sent to first logicmeans 46 via electrical connector 56 and to the electrical connector 62leading to the first solenoid via electrical connector 58.

FIG. 2 generally illustrates relay valve 40 having an upper housingportion 102 and a lower housing portion 204. Each housing portion ispreferably formed by casting a suitable metal for finishing as bymachining or the like, although other suitable casting or moldingmaterials are contemplated.

Upper housing portion 102 includes generally annular portion 108 havingan outer annular peripheral surface 108a and an inner annular bore 108bextending inwardly from first annular end 110 and terminating at innersurface 112a of annular endwall 112. First end 110 includes groove 110afor accommodating sealing O-ring 114. Outer surface 108a extendsupwardly from end 110 and terminates at and extends into outer surface112b of endwall 112. Annular bore 106 is centrally located in endwall112 and includes annular lip 116 having inner and outer annular surfaces116a and 116b respectively. Vertical passageways 118 and 120 are formedin endwall 112 and extend therethrough from inner surface 112acontinuing upwardly into extended portions 122, 124 respectivelyintegratedly formed with upper portion 102.

In FIG. 3, passageways 118, 120 terminate at openings 123, 125,respectively. Transverse or horizontal passageways 126, 128,respectively interconnect openings 123, 125 with vertical passageways130, 132 which, as shown in FIG. 2, terminate in enlarged openings orports 72, 74, respectively, adapted for being threadedly secured toappropriate high pressure fluid connectors to respectively accommodatefluid conduits 22 and 70.

Returning to FIG. 3, well known solenoids 134, 136 of the type generallyshown and described in U.S. application Ser. No. 369,966 filed June 14,1973 now U.S. Pat. No. 3,854,501, entitled "Antilock Brake System AndControl Valve Therefor" issued on Dec. 17, 1974 to John A. Machek andassigned to the assignee of this invention, are mounted in side by sideannular openings 101, 103, respectively, formed in upper portion 102 andhaving centroidal axes transverse to the centroidal axis of annular bore106. Openings 101, 103 extend inwardly from first end 105 and terminateat endwalls 107, 109, respectively. Threaded recesses 142, 144 areformed in endwalls 107, 109, respectively. Threaded mounting portions138, 140 of solenoids 134, 136, respectively, are secured intocorrespondingly threaded recesses 142, 144. Threaded recesses 142, 144are integratedly formed with openings 123, 125 respectively foraccommodating plunger sealing portions 146, 148 of solenoids 134, 136,respectively. Electrical connector 143 is appropriately mounted inhousing portion 102 for interconnecting electrical power supplied toreceptacle 145 with the conductive portions or coils 149 which surroundaxially reciprocable armatures 156 of the well known solenoids viaconductive flux plate 111. Coils 149 are insulatedly mounted in housingportion 102 by appropriate nonconductive insulators 147 in the wellknown manner. Also, plunger shaft portions 150, 152 of solenoids 134,136, respectively are provided to interconnect armatures 156 withsealing portions 146, 148 for sealing engagement with seating areas orlands 123a, 125a, respectively, formed at the intersecting portions ofopenings 123, 125 and horizontal passageways 126, 128, respectively.Exhaust passage 158 is formed in first extended portion 122 and includesrelatively large passage portion 160 integratedly and coaxially formedwith relatively small passage portion 162 so that exhaust passage 158interconnects plunger passage 164 with annular opening 101. In thismanner, first sealing surface 146a of solenoid sealing portion 146 mayseat against land 138a formed on threaded mounting portion 138 of firstsolenoid 134 to interrupt fluid communication between plunger passageway164 and opening 123 when in a first, or non-actuated position, or in thealternative, second sealing surface 146b of solenoid sealing portion 146may seat against land 123a to interrupt fluid communication betweenhorizontal passageway 126 and opening 123 when in a second or actuatedposition. Thus, plunger shaft 150 is normally biased by spring 166 sothat second sealing surface 146b is normally out of sealing engagementwith land 123a and fluid communication between passage 126 and opening123 is normally open. Plunger 152 extends through plunger passage 168 ofthreaded mounting portion 140 of second solenoid 136 mounted in annularopening 103. Sealing portion 148 is mounted on plunger shaft 152 andincludes first sealing surface 148a for sealing engagement with seatingarea 125a to limit fluid communication between horizontal passageway 128and opening 125 when in a first or non-actuated position, or in thealternative, second sealing surface 148b or solenoid sealing portion 148may seat against land 140a of threaded mounting portion 140 to openfluid communication between horizontal passageway 128 and opening 125when in a second or actuated position. Thus plunger shaft 152 isnormally biased by spring 170 so that first sealing surface 148a isnormally in sealing engagement with seating area or land 125a and fluidcommunication between passages 128 and opening 125 is normally closed.Nonconductive closure member 154 including receptacle 145 seats inrecess 105a formed in end 105 of upper portion 102 to position fluxplate 111 in recess 105a against displacement, the closure member beingsecured to the housing by some suitable means.

Lower housing 204, FIG. 2, is generally annular and includes uppersurface 202 including a centrally located aperture 206 therein forcoaxial disposition with bore 106 of upper housing 102. Recess 208 isformed at the intersection of outer annular periphery 214 and surface202 for accommodating lower annular end 110 of upper housing 102. Also,recess 210 is formed in upper surface 202 and extends downwardly intohousing 204. Threaded outlet or port 212 is formed in outer periphery214 for accommodating an appropriate fixture for conducting fluid underpressure from relay valve 40 to the vehicle brakes via conduit 48.Outlet 212 extends inwardly into lower housing 204 and intersects recess210. Threaded inlet or port 216 is formed in outer periphery 214 foraccommodating an appropriate fixture for conducting fluid under pressurefrom fluid pressure source 36 to relay valve 40 via conduit 68.

Stepped annular bore 218, FIG. 2a, is formed in lower housing 204 andextends from lower surface 220 toward its intersection with aperture 206in upper surface 202 to accommodate exhaust port or passageway 219through lower housing 204 coincidental with the centroidal axis thereof.Bore 218 includes first portion 218a intersecting with lower surface 220and extending inwardly to intersect with snap ring groove 218b. Retainergroove 218c of bore 218 is adjacent snap ring groove 218b and secondportion 218d extends inwardly from retainer groove 218c to itsintersection with third bore portion 218e forming shoulder 221. Annularseating portion 222 is formed at the on shoulder 224 intermediate ofbore portion 218e and aperture 206. First annular insert 226 ispreferably of metal and includes retaining surface 228, inner annularsurface 230 including inner groove 232, outer annular surface 234including outer groove 236, and upper surface 238 axially oppositeretaining surface 228 and interposed between inner and outer grooves232, 236. Second annular insert 240 is preferably of metal and includeslower surface 242 and axially opposed upper land or surface 244, innerannular surface 246 and outer annular surface 248. Annular piston orplunger 250 is preferably of metal and is generally tubular includinglower end 252 and upper flanged end 254. Intermediate tubular orcylindrical portion 256 interconnects upper and lower ends 254, 252,respectively and includes outer periphery 258 and inner periphery 260.Upper flanged end 254 includes resilient seal member 262 held in placeby metal retainer 259 forming a lower spring seating surface 259a offlanged end 254. Piston 250 may be inserted into bore 218 so that sealmember 262 engages annular seating portion 222. Second insert 240 isplaced in bore 218 so that inner annular surface 246 engages outerperiphery 258 of piston 250 and outer annular surface 248 engages boreportion 218d. Second insert 240 is axially retained by shoulder 221intermediate of bore portions 218d and 218e. First insert 226 is placedin bore 218 so that upper surface 238 engages lower surface 242 ofsecond insert 240, outer periphery 234 engages bore portion 218d andinner periphery 230 engages outer periphery 258 of piston 250. Resilientsealing O-rings 261, 263 are placed in inner and outer annular grooves232, 236, respectively. Retainer 264 is snapped into retainer groove218c to abut retainer surface 228 of first insert 226 and snap ring 266is snapped into snap ring groove 218b to abut and secure retainer 264 inplace. Spring 268 is disposed between spring seating surface 259a andupper land 244 to normally urge sealing member 262 into sealingengagement with annular seating portion 222.

Annular piston 306 is preferably of metal and includes upper surface 308including extended portion 310 centrally located and provided toslidably engage inner surface 116a of upper housing 102. O-ring groove312 is provided in annular periphery 310a for accommodating resilientO-ring 314 in sealing and sliding engagement with surface 116a. Outerannular peripheral surface 316 of piston 306 includes O-ring groove 318for accommodating resilient O-ring 320 in sealing and sliding engagementwith inner surface 108b of upper housing portion 102. Lower surface 322of piston 306 includes extended portion 324 axially opposed to extendedportion 310. Extended portion 324 terminates at annular seat 326engageable with sealing portion 262 of piston 250. Compression spring328 is disposed between surface 322 of piston 306 and upper surface 202of lower housing 204 for urging piston 306 upwardly away from lowerhousing 204 and toward housing 102 so that annular seat 326 does notnormally engage seal 262 of piston 250.

Main piston chamber 506 is formed by inner surface 112a of upper housing102, upper surface 202 of lower housing 204 and inner annular bore 108bof upper housing 102. Piston 306 sealingly slidably engages innerannular bore 108b via sealing ring 320 to separate main chamber 506 intoupper chamber portion 508 and lower chamber portion 510. The upperchamber is formed by inner surface 112a, upper surface 308 of piston 306and inner annular bore 108b. The lower chamber is formed by lowersurface 322 of piston 306, upper surface 202 and inner annular bore108b.

FIG. 4 includes the logic circuitry of first logic means 46 which is theelectronic control connected to receive first and second signals fromfirst and second transducers 42, 50, respectively. Inasmuch as firstsensor or transducer 42 senses fluid pressure in conduit 22 and producesa first signal proportional thereto and inasmuch as second sensor ortransducer 50 senses fluid pressure in conduit 48 and produces a secondsignal proportional thereto, the first logic means 46 is capable ofdiscriminately controlling communication of a second pressure impulse tothe trailer brakes (not shown) dependent upon impulse communication of afirst pressure from first valve 16 to second valve 40. It can be seenfrom the logic system of FIG. 4 that for example where the systempressure is within a range of 0-100 pounds per square inch (psi) thetransducers 42, 50 may produce a proportional signal within the ringe of0-10 millivolts (mv). Thus, in the application mode, for example,wherein a pressure of 50 psi is produced at application valve 16 andinto conduit 22, a proportional signal of 5 mv will be sent fromtransducer 42 to logic means 46 via connection 44. This signal entersthe logic means at line 44 and is sent to inverter 462 via line 402 andalso sent to adder 408 via lines 404, 406 and to comparator 412 vialines 404, 410. Thus, inverter 462, adder 408 and comparator 412 eachreceive a 5 mv signal from transducer 42. The 5 mv signal received byinverter 462 is inverted to a minus (-) 5 mv signal and sent to adder420 via line 418. At this point there is no significant pressure sensedat transducer 50 so that a zero (0) mv signal is realized by logic means46 relative to transducer 50. This 0 mv signal enters the logic means atline 52 and is sent to inverter 436 via line 422 and also sent to adder420 via lines 424, 428 and to comparator 430 via lines 424, 426. Thus,inverter 436, adder 420 and comparator 430 each received a 0 mv signalfrom transducer 50. The 0 mv signal received by inverter 436 is invertedto a minus (-) 0 mv signal and sent to adder 408 via line 438.

At this point adder 408 is receiving a 5 mv input signal from transducer42 and a -0 mv input signal from transducer 50 via inverter 436. Theadder, as is well known, will algebraically add the values of theseinputs and produce a resultant output signal which, in this case, is a 5mv signal which is sent to comparator 442 via line 440. Similarly, adder420 is receiving a -5 mv input signal from transducer 42 via inverter462 and a 0 mv input signal from transducer 50. Adder 420, as is wellknown, all algebraically add the values of these inputs and produce aresultant output signal which, in this case, is a -5 mv signal which issent to comparator 454 via line 452.

Comparators, as it is well known, can receive various signals andcompare them to produce either a signal of some value (e.g. 1) or nosignal (e.g. 0). Comparator 412 is provided to receive a predeterminedsignal from an external power source, e.g. a predetermined signal of 0.5mv to simulate a pressure sensed of 5 psi. Comparator 442 is provided toreceive a predetermined signal from an external power source, e.g. apredetermined signal of -0.25 mv to simulate a pressure sensed of -2.5psi. Similarly, comparators 432 and 454 are receiving signals of 0.5 mvand -0.25 mv, respectively. Thus, comparator 412 is receiving signals of5 mv and 0.5 mv, comparator 442 is receiving signals of 5 mv and -0.25mv, comparator 430 is receiving signals of 0.5 mv and 0 mv andcomparator 454 is receiving signals of -5 mv and -0.25 mv. In logicmeans 46, comparator 412 is provided to produce a signal of value (e.g.a 1 signal) if the value of the signal it receives via line 410 isgreater than the value of the signal it receives via line 414, and toproduce no signal (e.g. a 0 signal) if the value of the signal itreceives via line 414 is greater than the value of the signal itreceives from line 410. In this case, comparator 412 receives the signalof greater value from line 410 and thus produces a 1 signal communicatedto "and" gate 448 via line 416. Comparator 442 is provided to produce a1 signal if the value of the signal it receives via line 440 is greaterthan the value of the signal it receives via line 444, and to produce a0 signal if the value of the signal it receives via line 444 is greaterthan the value of the signal it receives from line 440. In this casecomparator 442 receives the signal of greater value from line 440 andthus produces a 1 signal communicated to and gate 448 via line 446.Comparator 430 is provided to produce a 1 signal if the value of thesignal it receives via line 426 is greater than the value of the signalit receives via line 432 and to produce a 0 signal if the value of thesignal it receives via line 432 is greater than the value of the signalit receives via line 426. In this case comparator 430 receives thesignal of greater value from line 432 and thus produces a 0 signalcommunicated to and gate 460 via line 434. Comparator 454 is provided toproduce a 1 signal if the value of the signal it receives via line 452is greater than the value of the signal it receives via line 456 and toproduce a 0 signal if the value of the signal it receives via line 456is greater than the value of the signal it receives from line 452. Inthis case comparator 454 receives the signal of greater value from line456 and thus produces a 0 signal communicated to and gate 460 via line458.

And gates, as it is well known, can receive both a 1 signal and a 0signal to produce either a resultant 1 signal or 0 signal. And gates448, 460 are provided to produce a 1 signal when each signal it receivesis a 1 signal and to produce a 0 signal when any signal it receives is a0 signal. At this point and gate 448 is receiving a 1 signal fromcomparator 442 and a 1 signal from comparator 412. Thus, gate 448produces a 1 signal. And gate 460 is receiving a 0 signal fromcomparators 430, 454. Thus, gate 460 produces a 0 signal.

"Nor" gates, as it is well known, can receive a 0 signal and change itto a 1 signal, and in the alternative can receive a 1 signal and changeit to a 0 signal. The 1 signal produced at and gate 448 is sent to andgate 474 via line 450, 478 and to nor gate 482 via lines 450, 476. Norgate 482 converts the 1 signal received from and gate 448 to a 0 signalwhich is sent to and gate 486 via line 484. The 0 signal produced at andgate 460 is sent to and gate 486 via lines 464, 466 and to nor gate 470via lines 464, 468. Nor gate 470 converts the 0 signal received from andgate 460 to a 1 signal which is sent to and gate 474 via line 472. Thusand gate 474 receives a 1 signal from and gate 448 and a 1 signal fromnor gate 470, whereas and gate 486 receives a 0 signal from and gate 460and a 0 signal from nor gate 482. As previously stated, the and gatesproduce a 1 signal if they receive only 1 signals and produce a 0 signalif they receive any 0 signal. Thus, it can be seen that and gate 474will produce a 1 signal along line 480, and and gate 486 will produce a0 signal along line 488. Any signal from and gate 474 is sent along line480 to a power amplifier 481 and then is transmitted along line 60 tosecond solenoid 136 which is normally closed. Any signal from and gate486 is sent along line 488 to a power amplifier 489 and then istransmitted along line 62 to first solenoid 134 which is normally open.

Still referring to FIG. 4, the above-described logic means 46 beingsimilar to those well known in tractor-trailer fluid pressure relaysystems, a novel dimension is contemplated by this invention due to thecoupling of the first logic means 46 with a known skid control logicmeans 54 via line 56 so that tractor-trailer fluid pressure relaysystems may be adapted to meet skid control requirements. Skid controllogic means 54 may be of the type shown and described in U.S. Pat. No.3,827,760 to Joseph E. Fleagle, issued on Aug. 6, 1974 on applicationSer. No. 218,378 filed Jan. 17, 1972 and entitled "Wheel Slip ControlSystem For Automotive Vehicles And The Like"; U.S. Pat. No. 3,842,355 toJoseph E. Fleagle, issued on Oct. 15, 1974 on application Ser. No.340,735 filed Mar. 13, 1973 and entitled "Signal Processing Circuit ForWheel Slip Control Systems", a division of the above-mentioned U.S. Pat.No. 3,827,760; U.S. Pat. No. 3,833,268 to Joseph E. Fleagle, issued onSept. 3, 1974 on application Ser. No. 223,579 filed Mar. 10, 1972 andentitled "Wheel Slip Control System For Automotive Vehicles And TheLike"; and U.S. Pat. No. 3,840,816 to Joseph E. Fleagle issued on Oct.8, 1974 on application Ser. No. 340,915 filed Mar. 13, 1973 and entitled"Wheel Speed Signal Processing Circuit For Wheel Slip Control Systems",a division of the above-mentioned U.S. Pat. No. 3,833,268; each of theabove-mentioned patents being assigned to the Assignee of the presentinvention and incorporated herein by reference. Also, line 54interconnects skid control logic 54 and line 62 for direct electricalcommunication between the skid control logic and normally open solenoid134. Thus, from the foregoing it can be seen that when impending skidconditions are sensed and transmitted to skid control logic means 54 vialine 66, that logic means can send a signal to nor gate 470 of firstlogic means 46 and directly to first solenoid 134 via line 62. Inaddition to the aforementioned capability of nor gates, such gates canreceive more than a single signal. When nor gates do receive pluralsignals and those signals are only 0 signals, the gate will produce a 1signal; and when any signal received is a 1 signal a 0 signal will beproduced. Of course, any signal or the absence thereof transmitted fromskid control logic 54 directly to line 62 via line 54 is unaltered.

A "deadband" portion is included in first logic means 46 and isgraphically illustrated in FIG. 5. The purpose of the deadband is topreclude simultaneous actuation of both solenoids 134, 136 within apredetermined band width. Without such a deadband it would be possiblefor both solenoids to be simultaneously actuated in which case the airsupply from reservoirs 18, 36 would be rapidly depleted. Suchsimultaneous actuation of both solenoids could conceivably occur whentransducers 42, 50 sensed equivalent pressures and sent identicalsignals to logic means 46. The deadband may be of a predetermined widthsuch as for example 5 psi representing a 5 mv signal (i.e. from minus2.5 psi to plus 2.5 psi) as shown in FIG. 5. Thus, the deadbandprecludes simultaneous actuation of both solenoids not where pressuressensed at both transducers are equivalent but when those pressures arewithin a predetermined pressure differential band width of, as in thiscase, 5 psi.

In FIG. 4, it can be seen that the deadband is provided in logic means46 due to the inclusion of a constant signal input of minus (-) 0.25 mvto simulate a pressure of minus (-) 2.5 psi at comparator 454 and asimilar input signal at comparator 442, and further due to the inclusionof nor gates 470 and 482. The deadband can be widened or narrowed byappropriately changing the values of the constant input signals atcomparators 454, 442. Thus, the values of the constant input signalsdetermine the width of the band whereas the inclusion of nor gate 470between and gates 460, 474, and the inclusion of nor gate 482 betweenand gates 448, 486 preclude simultaneously actuated signals fromreaching solenoids 136, 134, respectively.

The foregoing is illustrated in FIG. 5 where it is shown by the linedesignated B, the inverse of which is shown by the line designated C fordescriptive purposes, that where the pressure sensed at transducer 50 isgreater than that sensed at transducer 42, as the pressure differentialdecreases, the possibility of both solenoids 134, 136 simultaneouslyactuating is precluded within a predetermined deadband of 5 psi (i.e.minus 2.5 to plus 2.5). Similarly, as is shown by the line designated A,that where the pressure sensed at transducer 42 is greater than thatsensed at transducer 50, as the pressure differential decreases, thepossibility of both solenoids 134, 136 simultaneously actuating isprecluded within the predetermined deadband.

Operation

During the application mode, that is, when the vehicle operator appliesfoot pressure to pedal 64, fluid pressure is released from firstreservoir 18 through application valve 16 to the front tractor brakesvia conduit 23, to the rear tractor brakes via conduit 30 and to relayvalve 40 via conduit 22. Thus a first impulse of fluid pressure isproduced at first valve 16 and communicated toward second valve 40 viaconduit 22. The first inpulse may enter valve 40 at port 72 and passthrough a first passageway comprising passages 130, 126 into opening 123and further through passage 118 to upper chamber 508 to communicate withand cause a first downward force on upper surface 308 of piston 306.This downward force is opposed by an oppositely acting upward force dueto spring 328 acting on lower surface 322 of piston 306. However, due tothe remoteness of valve 40 relative to valve 16, a substantial delay isexperienced in communicating the first impulse to valve 40.

Under the above-described conditions, transducer 42 connected to conduit22 adjacent valve 16, senses a pressure that is relatively higher thanthe pressure sensed by transducer 50 connected to conduit 48 adjacentvalve 40. Thus transducer 42 and 50 produce signals proportional totheir respective pressures sensed. The signal from transducer 42 iscommunicated to logic means 46 via electrical connection 44 while thesignal from transducer 50 is communicated to logic means 46 viaelectrical connector 52. The signal from transducer 42 to logic means 46is transmitted much faster than the first impulse can be communicated tovalve 40 via conduit 22.

With the logic means 46 provided as hereinabove set forth a 1 signal issent from logic means 46 to solenoid 136 of valve 40 and a 0 signal issent to solenoid 134. The signal sent to solenoid 136 actuates thisnormally closed solenoid and opens a second passageway comprisingpassages 132, 128 into opening 125 and futher into passage 120 to admita second impulse of fluid pressure from second reservoir 36 to upperchamber portion 508 to communicate with and cause a second downwardforce on upper surface 308 of piston 306. This second downward forceprecedes the first force resulting from the first impulse to act onpiston 306. Since the tractor-trailer fluid pressure systems areinterconnected via conduit 38, the first and second impulses canequalize.

Fluid pressure from second reservoir 36 is in constant communciationwith inlet port 216 of valve 40. This fluid pressure is normallyprecluded from communication with the lower surface 322 of piston 306 inlower chamber 510 due to sealing member 262 and seating portion 222being urged into sealing engagement by spring 268. The second downwardforce is opposed by the force exerted by spring 328 and since lowerchamber 510 is in open fluid communication with the atmosphere viaexhaust port 219, piston 306 is forced downwardly so that annular seat326 of piston 306 engages sealing portion 262 of piston 250 to interruptfluid communication between lower chamber 510 and exhaust port 219 andopen fluid communication between lower chamber 510 and second container36 whereby a third impulse of fluid pressure at inlet 216 is admittedinto lower chamber 510. This third impulse can equalize with the firstand second impulses due to the interconnection of reservoirs 18 and 36.This immediately causes an upward force applied to lower piston surface322 sufficient to drive piston 306 upward in chamber 506 since fluidpressures acting on opposite sides of piston 306 are substantially equaland the fluid force on lower surface 322 is aided by the upward forceexerted by spring 328. When the third impulse of fluid pressure isadmitted into lower chamber 510 this causes the third impulse of fluidpressure to be almost immediately communicated to the trailer brakes viarecess 210, outlet 212 and fluid conduit 48. As a result a suddenpressure rise is sensed in conduit 48 by transducer 50 which transmits aproportional signal to logic means 46 via line 52.

The holding mode of this system follows the initial application modewhereby the vehicle operator can forseeably hold downward pressure onpedal 64 of application valve 16 and the third impulse of fluid pressurehas been communicated to the trailer brakes. The pressure rise sensed bytransducer 50 can increase to a pressure substantially equal to thepressure sensed by transducer 42. At this point it can be appreciatedthat, in view of the foregoing description of first logic means 46, whenpressure sensed by transducer 50 is at least as high as the pressuresensed by transducer 42, a 0 signal is produced from the first logicmeans and sent to second solenoid 136 along line 60 and a 0 signal issent to first solenoid 134 along line 62. A 0 signal to the secondsolenoid causes that solenoid to return to its normally closed positionthus interrupting communication of the second impulse from reservoir 36to upper chamber 508. However, upper chamber 508 remains in fluidcommunication with conduit 22 in which the first impulse was generated.Thus, the first impulse provides substantially the same pressure inupper chamber 508 as was provided by the second impulse. Fluid pressurechambers 508, 510 being exposed to substantially equal pressure, piston306 is provided to position itself within chamber 506 so that bothseating areas 326, 222 are in sealing engagement with sealing portion262 thus interrupting fluid communication between lower chamber 510 andinlet 216 and between chamber 510 and exhaust passage 219. Thus, thethird impulse of fluid pressure remains isolated between lower chamber510 and the rear trailer brake actuators. In this manner, the pressuressensed at transducers 42, 50 remain substantially equal.

The release mode of this system generally follows the holding modewherein, as hereinbefore discussed, pressures sensed at transducers 42and 50 are substantially equal. The release mode is caused by removal offoot pressure from pedal 64 by the vehicle operator. Such removal offoot pressure at valve 16 cuts off or interrupts the first impulse offluid pressure being supplied from first reservoir 18 to relay valve 40via conduit 22. Thus, transducer 42 immediately senses a pressure dropand sends a proportional signal to first logic means 46. At this pointtherefore, transducer 50 is sensing pressure higher than the pressuresensed by transducer 42 and is sending a signal proportional thereto tofirst logic means 46 via line 52. Therefore, it can be appreciated thatin view of the foregoing description of logic means 46, when pressuresensed by transducer 50 is higher than pressure sensed by transducer 42,a 0 signal is produced from the first logic means and sent to secondsolenoid 136 along line 60 and a 1 signal is sent to first solenoid 134along line 62. A 1 signal to first solenoid 134 actuates that solenoidfrom its normally open position permitting fluid communication betweenconduit 22 and upper chamber 508 via the first passageway to a closedposition whereby sealing surface 146b seats against seating area 123a tointerrupt fluid communication in the first passageway particularlybetween passage 126 and opening 123. As a result, fluid pressure inupper chamber 508 is permitted to exhaust back through passage 118 intoopening 123 and then through passage 164, exhaust passage 158 andultimately to atmosphere through unsealed solonoid chamber 101. Anyexcess pressure remaining in passage 126 and 130 is exhausted backthrough port 72 and conduit 22. Further exhausting of chamber 508 isaccomplished due to a pressure drop in chamber 508 which permitsrelatively higher pressure in lower chamber 510 to force piston 306upwardly. Thus, seating area 326 is urged out of sealing engagement withsealing portion 262 which permits pressure in conduit 48 to exhaustthrough outlet 212, recess 210, chamber 510 and ultimately to atmospherevia exhaust port 219.

The foregoing generally describes operational characteristics ofsimilarly known fluid pressure relay brake systems although theabove-described system includes a relay valve 40 and logic means 46having novel provisions incorporated therein.

With the advent of skid control systems, the known fluid pressure relaybrake systems were found to be incompatible therewith. The novel relayvalve 40 of this invention functions with the fluid relay brake systemsto give similar results to those given in known systems during thenormal application, holding and release modes, but due to the novelprovisions of the valve and first logic means 46, compatibility betweenthe fluid relay system and skid control systems is achieved.

Thus, during the application mode, as hereinabove set forth, pressuresensed at transducer 42 is greater than pressure sensed at transducer 50and proportional signals are sent by the transducers to first logicmeans 46. With the logic means 46 provided as stated above, it can beappreciated that nor gate 470 receives a 0 signal from and gate 460 vialines 464, 468. That 0 signal is converted to a 1 signal. Thus, a 1signal is produced at and gate 474 and solenoid 136 is actuated toultimately permit valve 40 to communicate fluid pressure from reservoir36 to the rear trailer brakes while a 0 signal is produced at and gate486 so that normally open solenoid 134 remains open to permit fluidcommunication between reservoir 18 and piston 306 of valve 40. However,should an impending skid condition exist, skid control logic means 54sends a 1 signal to nor gate 470 via line 56 and also a 1 signal is sentdirectly to first solenoid 134 via line 58 to line 62. As earlierdescribed, nor gate 470 having received multiple signals any of which isa 1 signal, then a 0 signal is produced. Thus, the result is that a 0signal is produced at and gate 474 to deactuate the actuated solenoid136 so as to omit fluid pressure communication from reservoir 36 to therear trailer brakes. Also, a 1 signal is sent directly to normally opensolenoid 134 via lines 58 and 62 so that solenoid 134 is actuated toclose thus omitting fluid communciation between reservoir 18 and piston306 of valve 40. Thus, the novel provisions of the interconnection oflogic means 46 and 54 and the novel provisions of relay valve 40 providea simulated release mode in the fluid pressure relay system even throughfoot pressure is still being applied to pedal 64. If, however, noimpending skid conditions exist, it can be seen that interconnection oflogic means 46 and 54, when logic means 54 is producing 0 signal, has noeffect on the normal functioning of the relay system.

During the holding mode, as hereinbefore set forth, pressure sensed attransducers 42 and 50 are substantially equal and proportional signalsare sent by the transducers to first logic means 46. With logic means 46provided as stated above, it can be appreciated that nor gate 470receives a 1 signal from and gate 460 via lines 464, 468. That 1 signalis converted into a 0 signal. Thus, a 0 signal is produced at and gate474 and solenoid 136 is deactuated to ultimately limit valve 40 tofurther communicate fluid pressure from reservoir 36 to the rear trailerbrakes while a 0 signal is produced at and gate 486 so that normallyopen solenoid 134 remains open to permit fluid communication betweenreservoir 18 and piston 306 of valve 40. However, should an impendingskid condition exist, skid control logic means 54 sends a 1 signal tonor gate 470 via line 56 and also a 1 signal is sent directly to firstsolenoid 134 via line 58 to line 62. As earlier described, nor gate 470having received multiple signals any of which is a 1 signal, then a 0signal is produced. Thus, the result is that a 0 signal is produced atand gate 474 as before so as to have no effect on solenoid 136 and omitfluid pressure communication from reservoir 36 to the rear trailerbrakes. Also, a 1 signal is sent directly to normally open solenoid 134via lines 58 and 62 so that solenoid 134 is actuated to close thusomitting fluid communication between reservoir 18 and piston 306 ofvalve 40. Thus, the novel provisions of the interconnection of logicmeans 46 and 54 and the novel provisions of relay valve 40 provide asimulated release mode in the fluid pressure relay system even thoughfoot pressure is still being applied to pedal 64. If, however, noimpending skid conditions exist, it can be seen that interconnection oflogic means 46 and 54, when logic means 54 is producing 0 signal, has noeffect on the normal functioning of the relay system.

Obviously, during the release mode, no impending skid conditions aresensed inasmuch as the release mode is the mode during which there is nobraking action occurring at application valve 16.

With logic means 46 provided as hereinabove described the minus (-) 0.25mv constant signal input at comparator 454 and a similar signal input atcomparator 442 can alter the signal received from adders 420, 408,respectively. Also nor gates 470, 482 can alter the signals they receiveand send on to and gates 474, 486, respectively. As a result, thepotential simultaneous actuation of both solenoids is precluded.

The foregoing has described a system and a valve for use therein to makethat system compatible with skid control systems in tractor-trailercombinations. It is anticipated that modifications and variations of thepresent invention are possible in the light of the above teachings. Itis, therefore, to be understood that within the scope of the appendedclaims the invention may be practiced otherwise than as specificallydescribed.

I claim:
 1. A relay valve for use in an air brake system wherein brakeactuators are operated by fluid pressure, the valve comprising:firstport means in the valve for receiving a first impulse of fluid pressurefrom a first source; second port means in the valve for receiving asecond impulse of fluid pressure from a second source; first solenoidmeans normally opening the first port for permitting the first impulseof pressure to enter the valve; and second solenoid means normallyclosing the second port and operably connected for permitting the secondimpulse of pressure to enter the valve simultaneously with the firstimpulse.
 2. A relay valve for use in an air brake system wherein brakeactuators are operated by fluid pressure, the valve comprising:firstpassage means formed in the valve for permitting a first impulse offluid pressure to enter the valve; means in the first passage meansnormally opening the first passage and operable under preselectedconditions to close the first passage; second passage means formed inthe valve; and means in the second passage means normally closing thesecond passage and operable under preselected conditions to open thesecond passage for permitting a second impulse of fluid pressure toenter the valve simultaneously with the first impulse.
 3. The relayvalve of claim 2, wherein:the first passage means including exhaustmeans for exhausting fluid pressure to atmosphere.
 4. The relay valve ofclaim 3, wherein:the means in the first and second passage means,respectively, each comprise a solenoid.
 5. A relay valve for use in anair brake system wherein brake actuators are operated by fluid pressure,the valve comprising:a piston chamber formed in the valve; piston meansoperable for reciprocating in the chamber in response to fluid pressureacting thereon; first passage means formed in the valve for permitting afirst impulse of fluid pressure to enter the valve and communicate withthe piston; closure means reciprocable in the first passage meansnormally opening the first passage and operable under preselectedconditions to close the first passage for interrupting fluid pressurecommunication with the piston; second passage means formed in the valve;and closure means reciprocable in the second passage means normallyclosing the second passage and operable under preselected conditions toopen the second passage for permitting a second impulse of fluidpressure to enter the valve and communicate with the pistonsimultaneously with the first impulse.